Charging that mice infestation in school cafeterias has spiraled out of control, union officials yesterday urged Mayor Bloomberg to triple the number of exterminators.

The plea came a day after The Post reported that 360 lunch rooms were rife with rodents, and 111 were so filthy that they flunked health inspections.

And 530 school cafeterias – nearly half – were slapped with violations for shoddy maintenance and filthy conditions that invited pests.

The city Department of Education has a private contractor and in-house pest-control unit to respond to rodent problems.

But the number of exterminators in the department’s pest-control unit has dropped from 21 to 16 over the past year, said Lillian Roberts, executive director of District Council 37. “They cut back on the exterminators. They didn’t replace them. The situation now tells you there is nobody at home,” Roberts said.

Roberts said she’s requesting a meeting with Schools Chancellor Joel Klein to demand a boost in the pest-control staff to 48.

“It’s getting cold now. The mice and roaches come inside,” she said.

Roberts also charged that the schools’ private pest-control firm, USA Exterminator, has failed to fix the problem.

Martin Oestreicher, the department’s director of school-support services, vowed to slash the number of rodent violations by 25 percent. He said better coordination and training – not more staffing – will turn things around.